This invention relates to memory-disk drives as used in computer systems. Such disk drives utilize a memory-disk cartridge which is separate from and removable from the memory-disk drive. The memory-disk drive has a spindle on which the rotating memory-disk element is mounted by means of a mounting hub magnetically retained by an attached armature. More specifically, this invention relates to a testing device for such memory-disk-cartridge hubs to aid in both the design process and the testing of completed units. The hub tester works by providing variable mechanisms to simulate the conditions of mounting on an actual memory-disk drive spindle.
There is relatively little prior art relating to this type of specialized equipment. However, earlier testing devices did not provide for variation in magnetic field strength to test a full range of resultant retaining forces. Similarly, the prior art did not provide an authentic reproduction of the hub-diaphragm action in testing magneticaly retained disk-cartridge hubs. Other features not present in the prior art but present in the disclosed invention relate to stress testing and determination of failure modes of the device under test. A further requirement of testing is that the unit be capable of testing different hub-assembly designs and that this be the result of a fairly simple and rapid testing procedure. Further requirements of such a testing device would be high reliability as to measurement results, accuracy, and repeatability. It is believed that the present invention fulfills the various requirements for hub testing in a single unit in a way not previously obtainable except as the result of using several different testing devices for separate tests.
One significant problem with the prior art is that the stress distribution magnetically applied to the hub armature did not closely resemble that existing during actual hub operation. Consequently, even though a hub assembly might withstand the total force considered necessary in an appropriate specification, there was no assurance that the peak tensile stress existing between the armature and attached hub during actual operation had been reached during a test cycle. Consequently, test results were inconclusive in some situations. A specific example of a problem with the prior art is illustrated by a test in which an armature withstood a standard proof test of 400 pounds but subsequently failed during a final-assembly operation under a tensile force no greater than 40 pounds. Obviously such a test is misleading, and the present invention is directed towards a hub tester which provides meaningful test results.